Radio-telecommnucation equipment for simplex or duplex traffic with uniselector switch



May 5, 1959 G. A. RADIO-TELECOMMUNICATION EQUIPMENT FOR SIMPLEX OR DUPLEX TRAFFIC WITH UNI-SELECTOR SWITCH Filed Feb. 23, 1954 MATHIEU 2,885,540

2 Sheets-Sheet l INVENTOR AGENT G. A. MATHIEU 2,885,540 RADIO IELECOMMUNICATION EQUIPMENT FOR SIMPLEX 19 O5 DUPLEX TRAFFIC WITH UNI-SELECTOR SWITCH 2 Sheets-Sheet 2 May 5, 1959 Flled Feb 25,

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RADIO-TELECOMMUNICATION EQUIPMENT FOR SIMPLEX UR DUPLEX TRAFFIC WITH UNI- SELE'CTOR SWITCH Gaston Adelin Mathieu Hambur German assi nor,

. by mesne assignments, to Norm American Pinups sompany, Inc, New York, N.Y., a corporation of ll eiaware Application February 23, 1954, Serial No. 411,803 Claims priority, application Germany February 21, 1953 4 Claims. (Cl. 250-6) This invention relates to radio-telecommunication equipments for simplex or duplex traffic on a plurality of fixed carrier-wave frequencies of the megacycle range and more particularly to equipments operating with mobile subscribers stations such as used, for example, on behalf of the police, the fire brigade, for the road guard, local radiobroadcast and for military purposes, in which it is possible to talk through three to ten channels or more. Since use is then made of a large number of carrier wave frequencies located in comparatively close proximity to one another, such a transmitting and receiving equipment is in most cases controlled for each channel by a correspondingly tuned crystal.

in the known devices of this kind, the said crystals are switched on and off by means of a switch commonly provided on one side of the housing and in which two or more multiple switches of low electrical capacity such as used, for example, in radio-sets are arranged one after another in screened positions and operated through the same shaft. More particularly in the case of mobile devices installed in motor cars, vessels and the like, it is frequently necessary to provide a remote control, since the device cannot, as a rule, be arranged in direct proximity to the operator due to lack of space. Such a remote control may be effected, for example, with the use of flexible shafts. However, such shafts have not been found to be reliable in time and furthermore the mounting thereof imposes requirements which cannot always be readily fulfilled. Such shafts, for example, cannot be formed into arcs of small radius of curvature without any further expedients and their operation becomes more difficult as the flexible shaft exhibits more curvatures.

A further possibility consists in the use of relays, 'by which the transmitter and receiver crystals are switched on and off respectively. This solution has not proved efiicacious either, the more so as the electrical capacity of the contacts of the relays with respect to earth increases with the number of speech channels and as a harmful natural capacity is connected parallel to the crystals. Furthermore, such relays are not sufiiciently secure in operation so far as they are incorporated in motor cars and thus subject to considerable vibrations. The use of particular small relays reducing the capacity of the contacts of the relay does not provide a solution, since such component parts of special make are expensive and such small relays often fail, if very weak high-frequency currents are to be switched on and off.

The object of the invention is to provide a radiotelecommunication equipment of the kind mentioned in the preamble in which the said switching difficulties are avoided in a simple manner.

The device according to the invention is characterized by a uni-selector switch for remotely controlled selection of the transmitting and receiving crystals and as the case may be, for making further connections, which switch is substantially constituted by component parts normally sold in commerce and in which the wipers and contact series associated with the transmitter portion and the receiver portion are decoupled by a screening plate which is incorporated in the contact bank and is grounded for high-frequency current and transverse to the shaft of the switch, which screening plate projects radially beyond the contact members and is electrically connected to the shaft of the switch by means of metallic discs, preferably of copper sheet, which are secured to the said shaft and resiliently engage the screening plate.

Such a selector switch is preferably of such a design that the individual wipers and the contact series to be hunted thereby have comparatively small capacities between them and with respect to the screening plate by the interposition of existing insulating parts.

This results in a uni-selector switch of the kind suitable for the above-mentioned purposes, which on the one hand fulfills the electrical requirements to be imposed and, on the other hand, is constituted almost completely by reliable component parts which are known and normally sold in commerce, which influences very favourably its cost. Mutual capacitive coupling of the individual contact series, more particularly of the contact series associated with the receiver crystals and the transmitting crystals, is prevented by the interposed screening plate, whilst the capacities of the individual contacts with respect to ground are substantially become negligible as a result of the spacings which are considerably increased as compared with the normal design.

The use of such uni-selector switches affords the possi- 'bility of introducing many switching and control methods known in automatic telephony. More particularly it has been found to be efficacious to utilise the uni-selector switches for automatically finding one operating transmitter out of two or more transmitters having different carrier-wave frequencies. The switch is kept moving with the use of a suitable device, for example a relay interruptor (whereby the receiving crystals corresponding to the various transmitting frequencies are switched-over), until a relay energised by the action of the carrier-wave frequency concerned, which relay is included, for example, in the anode circuit of the limiter tube of a receiver, is energised and brings the switch to a standstill.

In order that the invention may be readily carried into effect, it will now be described with reference to the accompanying drawings showing diagrammatically, by way of example, several embodiments thereof.

Fig. la is a plan view of, and Fig. 1b is a side view of, a uni-selector switch for use in the equipment according to the invention.

Fig. 2 shows the circuit diagram of an equipment according to the invention in which the transmitting and receiving crystals are operatively connected into circuit with the use of a calling-dial of the kind usually employed in telephony.

Fig. 3 shows a further switching device in which the radio-telecommunication equipment, after the receiver has been removed, automatically adjusts itself to the carrierwave frequency of one at that moment operative transmitter out of two or more transmitters having different carrier-wave frequencies.

Fig. 1 shows that the uni-selector switch in the device according to the invention substantially comprises component parts normally sold in commerce and that it is distinguished from known types solely by the fact that the contact series 1 and 2 associated with the transmitter and the receiver are separated by a metallic screen ing plate 3, which projects beyond the soldered extremities of the contacts. The screening plate 3 is connected for high frequency to ground, so that the contact series 1 and 2 are wholly decoupled capacitively. In addition to the said contact series there may be provided one or more further contact series 4, which may be used, for example, for controlling the switch for signalling purposes and the like.

The shaft of the switch carries two resilient discs 5, 6 of copper sheet, which are connected to the shaft and resiliently engage the screening plate 3. The discs serve to complete the screening. Furthermore, the spacing between the contact series 1 and 2 on the one hand and the screening plate 3 on the other hand is considerably larger than is normal in an uni-selector switch for automatic telephony due to superposition of a corresponding number of insulating intermediate layers 7 of the usual shape. Similarly, the axial spacing between the wipers 8, 9 and 10 is increased to the same extent by the interposition of spacers 11 of insulating material. The switch may, of course, comprise auxiliary contacts, which are not shown in the figure.

One embodiment of a radio-telecommunication equipment according to the invention is shown diagrammatically in Fig. 2. In this equipment it is possible, after the receiver 15 has been removed, to adjust the uni-selector switch by means of a normal telephone-dial 16 so as to select at the transmitting and the receiving end the quartz crystals which have to be switched in for the desired carrier-Wave frequency, whereupon after the counter-station has answered it is possible to talk on this carrier-wave frequency or to listen on the second associated carrier-wave frequency. The equipment is furthermore of such a design that the switch automatically moves on to its rest position after the receiver has been replaced.

When the receiver 15 is removed, the A- and B-relays, the latter of which operates with retardation, are energised, thus preparing the circuit of a rotary magnet D, since the contact b has been switched upwards and the back contact a is open. When the telephone-dial is turned up, the nsa-contact is closed in the usual manner and when the dial runs back the nsi-contact gives the dialling pulses to the A-relay, the resultant actuation of the back contact a causing the switch to perform the corresponding number of steps with the use of the rotary magnet D. The wipers d and d are thus adjusted to the transmitting and receiving crystals Q Q which are associated with the number that is dialled.

The transmitter comprises an oscillator 0 which is stabilised with a selected crystal Q and transmits its high-frequency oscillations to a modulating stage M0. The oscillation is modulated therein by the speech-frequency currents of the receiver after being amplified in an amplifier V and then transmitted to a frequencymultiplying stage V which controls a transmitting output stage P.

The associated receiver comprises an input amplifier V a mixing stage Mi, an intermediate frequency amplifier V a demodulator De and a low-frequency amplifier V which passes the incoming speech currents to the telephone. The mixing stage Mi is coupled to an oscillator 0 which, in turn, is connected by way of a wiper d to a receiving crystal Q selected by this wiper and which is stabilised by the said crystal.

For establishing the connection between the microtelephone circuit and the telephone circuit with the amplifiers V and V provision is made of a four-wire termination transformer C which is closed by means of an artificial line N and which permits separation between outgoing and incoming speech currents in known manner.

If, after termination of the call, the receiver is replaced, the subscribers loop is opened and the relays A and B are again de-energised. Since relay B is of the retarded type, relay A is de-energised first and the rotary magnet D thus receives via the closing back contact a a current pulse which is limited by the b contact which is de-energised afterwards. The switch thus performs another step, which does not matter, however, since the switch is bound immediately thereafter i.e. is restored to its initial position. This is brought about by the fact that at the same time as the contact b is de-energised, the B-relay is energised by way of the contact path d and switches on the uni-selector switch step by step in known manner until the wiper d has reached the insulated zero contact. The whole of the device then again occupies its initial position and is again ready for operation. The movement of the switch to its initial position is necessary of course, in order to be able to allot to each figure on the dial a certain carrier-wave frequency.

Fig. 3 shows another embodiment in which the same reference numerals are used so far as they indicate parts similar to those of Fig. 2. In this switching device the switch is made operative upon removing the receiver and scans the carrier-wave frequencies that enter into consideration until a transmitter operating at that time has been found. The device remains tuned to this carrier wave and a call may take place. When the receiver is replaced, the switch homes in a similar manner as in the example above described, thus restoring the device to its initial position. The receiver of the device under consideration is distinguished from the above described by the provision of a limiter B which may also be present in the receiver of Fig. 2, but which has not been mentioned with reference thereto.

When the receiver is removed, the R-relay, which energises the V-relay by way of its change-over contact r is energised and this via the path ground-r -b -d-vrelay-negative terminal. The rotary magnet D of the switch is thus energised and switched on step by step in known alternation of the contacts b and d, so that all pre-set frequencies are hunted in succession. If a transmitter is found on one of these frequencies, a current variation determined by the carrier wave of the transmitter concerned occurs in the limiter stage B which current variation causes energisation of the B-relay. For this purpose the winding of this relay may be included, for example, in the anode circuit of the limiter tube. With the energisation of the B-relay the b -contact is opened and thus the switch stopped. Subsequently a call with the station found can now take place.

After the call is over, the microtelephone is replaced, the subscribers loop is thus interrupted and the R-relay 1s de-energized. Since the wiper b in the meantime no longer engages a free contact, the V-relay is energised again by change-over of the r -contact, thus causing homing of the switch. It will be evident that the device may be such that the velocity of the switch during seeking materially differs from that during the homing movement and furthermore highly divergent problems may, as a rule, be solved with the uni-selector switch in the manner known for the automatic switching technique.

What is claimed is:

1. A mobile radio telephone system comprising a transmltter section having a plurality of tuning elements, a receiver section having a plurality of tuning elements, and a uni-selector switch comprising an elongated rotary shaft and two switching sections spaced apart along the axis of said shaft, each said switching section comprising a set of fixed contacts arranged arcuately about said shaft and a wiper contact adapted to selectively contact said fixed contacts when said shaft is rotated, electrical connections between said transmitter tuning elements and one of said switching sections, electrical connections between said receiver tuning elements and the other of said switching sections, a screening plate fixedly positioned perpen dicular to said axis between said switching sections and extending radially outward from said shaft beyond said fixed contacts, and a conductive disc attached concentrically on said shaft between said switching sections and slidably engaging said screening plate.

2. A rotary switch assembly comprising an elongated rotary shaft and two switching sections spaced apart along the axis of said shaft, each said switching section comprising a set of fixed contacts arranged arcuately about said shaft and a wiper contact adapted to selectively contact said fixed contacts when said shaft is rotated, a screening plate fixedly positioned perpendicular to said axis between said switching sections and extending ra dially outward from said shaft beyond said fixed contacts, and a conductive disc attached concentrically on said shaft between said switching sections and slidably engaging said screening plate.

3. A switch assembly as claimed in claim 2, in which said conductive disc comprises resilient material and resiliently engages against the surface of said screening plate.

4. A switch assembly as claimed in claim 2, including a second conductive disc positioned concentrically on said shaft between said switching sections and engaging said screening plate, said conductive discs comprising resilient material and resiliently engaging against opposed surfaces of said screening plate, respectively.

References Cited in the file of this patent UNITED STATES PATENTS 2,113,961 Hotopp Apr. 12, 1938 2,157,576 Schneider May 9, 1939 2,419,986 Brown May 6, 1947 2,522,715 Graybill Sept. 19, 1950 2,584,120 Fyler Feb. 5, 1952 2,657,266 Hoth et al. Oct. 27, 1953 2,762,925 Selbmann et al. Sept. 11, 1956 

